Speed responsive switch mechanism for actuating a pair of sequentially operated switches



Dec. 21, 1965 w. J. WILLIAMS 3,225,157

SPEED RESPONSIVE SWITCH MECHANISM FOR AGTUATING A PAIR OF SEQUENTIALLY OPERATED SWITCHES Filed April 23, 1964 United States Patent SPEED RESPUNSIVE SWITCH MECHANISM FOR ACTUATING A PAIR OF SEQUENTIALLY OPER- ATED SWITCHES William J. Williams, 2800 Black Hawk Road, Wilmette, Ill. Filed Apr. 23, 1964, Ser. No. 362,103 2 Claims. (Cl. 200-80) This invention relates to a speed responsive switch and particularly to a switch including an improved linkage mechanism for selectively controlling switches in accordance with the rotational speed of a drive shaft in the mechanism.

The mechanism of the present invention is particularly well suited for opening, closing, or transferring circuits in accordance with predetermined speeds applied to the drive shaft of the mechanism and is an improvement over that mechanism disclosed and claimed in my United States Patent No. 2,779,836.

It is a general object of the present invention to provide an improved speed-responsive mechanism for rotating drive shafts in which a plurality of switches are sequentially actuated as the rotational speed of a drive shaft increases above or decreases below preselected speed conditions.

A more specific object of the invention is to provide a new and improved speed-responsive mechanism for operating at least a pair of switches in which the difference between the switching speeds for the pair of switches may be held constant, but wherein the switching speeds may be selectable over a wide range.

A further specific object of the invention is to accomplish the above and other objects by a speed-responsive switch having a lever which is mounted about a fixed axis at one end and is acted upon at differing points by a plurality of force means and by a speed translating device, and this lever in turn operates upon at least a pair of switches.

Further objects and features of the invention pertain to the particular arrangement and structure wherein the above-identified objects and other objects of the invention are attained.

The invention, both as to its structure and mode of operation, will be better understood by reference to the following disclosure and drawings forming a part thereof, wherein:

FIGURE 1 is a top plan view of a switch mechanism in accordance with the present invention;

FIGURE 2 is a sectional view taken along line 22 of FIGURE 1;

FIGURE 3 is a sectional view taken along line 33 of FIGURE 1;

FIGURE 4 is a cross-sectional view of a pressure assembly or biasing assembly for the mechanism of FIG- URES l3;

FIGURE 5 is a perspective view of the switch assembly for the mechanism of FIGURES 1-3; and

FIGURE 6 is a schematic representation of the mechanism of FIGURES 13.

Turning now to the drawings and referring specifically to FIGURES 1 through 3, there is shown therein a switching mechanism 10 in accordance with the present invention.

Specifically, the switching mechanism 10 includes a housing 20, a centrifugally operated axially movable speed translation device 40, an operating lever 50, a switch assembly 60, and an adjustable biasing assembly 90. The vertical axial force of the speed translator 4% is dependent upon its speed of rotation, and this force operates pivotally against the adjustable biasing assembly 90 and the operating lever 50, which lever in turn operates against the switch assembly 60. The adjustable biasing assembly 90 also acts upon the operating lever 50, and may be adjusted to provide a wide range of input speeds at which the switch assembly 60 will be actuated.

The housing comprises a cylindrical container adapted to support and protect the operating parts. On its upper surface 26 there are provided a number of standard electrical connectors 21. Both the switch assembly 60 and the adjustable biasing assembly 90 are mounted through holes in the upper surfaces 26 of the housing 20. At one side of the upper surface 26 there is threadably secured a machine screw 22 which secures the base of a U-shaped bracket 23 to the housing 20. The sides of the bracket 23 extend downward into the interior of the housing 20 and have through their ends a pin 24. The pin 24 forms an axis 25 by fitting through a corresponding hole at one end 52 of the operating lever 50. In this manner, the operating lever 56 is rotatably secured about the fixed axis 25.

The operation of the speed translation device and its construction may be more fully understood by reference to my US. Patent No. 2,779,836. Basically, it comprises a shaft 41 which is imparted with the rotational input speed to be sensed. The shaft 41 is axially displaced toward the operating lever 50 bythe operation of the pivoted weights 42 and 43, whose centrifugal force component is exerted through lugs 44 and 45 upon the shaft 41. The rotational component of the shaft 41 is handled by a thrust bearing 46. The pointed end 47 on the upper surface of the thrust bearing 46 makes a pin connection with the point 51 on the operating lever 50. Variations in the input rotational velocity imparted to the shaft 41 result in a corresponding variation in the upward force applied at point 51 on the operating lever 50.

The operating lever is an elongate strip of metal or other suitable material. On end 52 is formed so as to attach to the pin 24 parallel to the plane of the lever 50 and pivot the lever about the axis 25, as described above. At a first predetermined distance on the operating lever 50 from the axis point 25 there is provided at the point 51 an upward-formed indentation 53. The indentation 53 provides the recess into which the pointed end 47 of the speed translator 40 fits. At a second predetermined distance along the operating lever 50 from the axis 25, at a point 55, there is preferably provided a cone 54 of metal or other suitable material, secured by welding or the like. The lever 50 passes through the switch assembly 60, and there the cone 54- contacts an indentation 64 in a pressure plate 61. A third point of contact 56 occurs near the extremity of the operating lever 50 furthest from the axis 25. At this point 56 the lower pointed extremity of the biasing assembly 90 pivotally contacts an indentation 57 in the operating lever 50.

It will be observed by the above that the operating lever Si i acted upon by the following elements: The axis pin 24, which rotatably secures it at end 52 at the fixed axis 25; the pointed end 47 of the control member 40 which exerts an upward force at point 51; the pressure plate 61 which exerts a downward force at point and the biasing assembly 90 which exerts a downward force at point 56. However, the rotational movement of the lever 50 is preferably limited between two extremes by, for example the shoulders 77 and 79 in the switch assembly 60. Each of the above forces on the lever arm create a moment upon the lever arm equal to the amplitude of the force times the distance at which it acts from the lever axis.

The switch assembly is adapted to provide an electrical output responsive to the level of rotational speed of the input shaft 41, preferably by means of the actuation of a pair of conventional electrical switches 62a and 62b.

The source of the force and movement components needed to actuate the switches is the speed translation device 40, as described above. The operating lever 56 serves to transmit this force and movement in a desirably modified manner by means of the leverage action of the lever 56 acting on the pressure plate 61 at the point 55. The pressure plate 61 is preferably a thin strip of metal or other suitable material mounted so as to pivot at its mid-point from an upward indentation 64 which receives the cone 54 on the lever 50. The vertical movement of the pressure plates i limited by the shoulders 63 of an opening 66 in each end of the switch assembly.

Coacting upon the pressure plate 61 within the switch assembly 60 are a pair of downwardly extending springloaded pressure assemblies 65a and 6512. Each of the pressure assemblies 65a and 65b contains movable pins 76a and 76b, each contacting one end respectively, of the pressure plate 61 at corresponding indentations 67a and 67b. The corresponding switches 62a and 62b, with their respective downwardly extending operating rods 6% and 6%, are mounted above opposite sides of the pressure plate 61. Under these operating rods are corresponding upwardly formed indentations 71a and 71b in the pressure plate 61 to push against the operating rods when the pressure plate moves upwardly sufficiently. As seen in FIGURE 4, each of the spring-loaded pressure assemblies 65a and 65b comprises a coil spring 74 pressing down on the upper end of the pin 76, both the spring 73 and pin 76 slidably secured inside a body 74 which is locked to the housing by means of a threaded nut and washer arrangement. A conventional screw adjustment 75 is preferably provided to adjustably compress the coil spring 73, and thereby adjust the force necessary for the pressure plate to push against the pin 76 to move it upward into the body 74 against the force of the coil spring 73. By varying the settings of the respective screw adjustments 75a and 75b in the two pressure assemblies 65a and 65b, one pin 76a or 76b will be forced upward more readily than the other.

The switch assembly is designed so that when sufficient upward force is applied by the lever 50 to the pressure plate 61 it will move upward, forcing one of the pins 76:: or 76b upward (whichever has the least spring force applied to it), thereby allowing that corresponding end of the pressure plate to tilt upward. When the end of the pressure plate has moved upward sufiiciently, one of the indentations 71a or 711) contacts the operating rod of one switch and actuates it. Then when sufiicient additional force is applied to the pressure plate 61 its other end will also move upward, thereby actuating the other switch. The difference between the force acting upon the pressure plate suflicient to move the pressure plate upward to actuate the first switch and the additional force necessary to move it further upward to actuate the second switch correspondings to a difierence in input speeds which may be referred to as the switch differential of the two switches. It can be seen that the switch differential may be adjusted by varying the screw adjustments 75a and 75b. This changes the force necessary to operate each switch and accordingly the input speeds to which each of the switches are responsive. The electrical terminals of the switches are connected by means of wires 80 to the various electrical connectors 21. g

The adjustable biasing assembly 90 is preferably identical to the pressure assembly 65a and 65b as described above. Thus, the bias 9t) exerts a downward force through its pin 92 on the operating lever 50 and this force may be adjusted by a screw adjustment means 95. The downward moment provided by this force acts counter to the upward moment provided by the action of the speed translation device 4%. Thus, to increase the rotational input speed at which the switch assembly 60 is to actuate it is necessary only to adjust the screw adjustment 95 to increase the bias force. It is not necessary to adjust the pressure assemblies 65a or 65b. Hence, the switch differential discussed previously may remain unchanged. By locating the point of contact 56 where the biasing assembly acts on the lever 50 at a greater distance from the axis 25 than the point of contact 51 with the speed translator, a moment advantage is provided for the biasing assembly, thereby providing more sensitive and wider speed range adjustment with the biasing assembly.

The operation of the mechanism 10, referring particularly to FIGURE 6, is described below. FIGURE 6 schematically illustrates a lever arm 101 fixed at one end for rotation about an axis 102. F represents the downward force exerted by the adjustable biasing assembly 90, acting on the lever arm at a distance X from the axis. Similarly F and F both acting at a distance X from the axis, represent the downward forces due to the pressure assemblies 65a and 65b. F acting at a distance X from the axis represents the upward force exerted on the lever by the speed translation device 40. The sum of the moments tending to rotate the lever downward may be expressed as F X +(F +F ')X and the opposing moment tending to rotate the lever upward may be expressed as F X The forces F F and F are normally adjusted by means of the respective screw adjustments so that the sum of the moments tending to rotate the lever downward exceeds the upward moment until the input speed at which it is desired to actuate the switch assembly is reached. Since the lever is thereby normally subject to moments which are not in equilibrium, a first equilibrium position is provided by the limit 103 (corresponding to the shoulder 79 in the switch assembly 60). Contrarily, when the input speed exceeds the preset switching speed range, so' that F X exceeds F X +(F +F )X a second limit 104 (corresponding to the shoulder 77) provides a second equilibrium position. The input speed at which the speed translation device 40 will cause the operating lever 101 to move from the first to the second equilibruim position may be changed simply by increasing or decreasing F by means of the screw adjustment 95, because an increase in the moment F X must be overcome by a corresponding increase in the moment F X The electrical switches are actuated sequentially during the movement of the lever from the first to the second equilibrium positions in the manner previously described, threby connecting or disconnecting the electrical connectors 21 and providing the desired signal to the equipment to which the mechanism is connected.

A significant advantage of the operating lever 50 to the improved operation of the mechanism of the invention relates to the fact that while, as discussed above, the input speed response may be changed by means of the biasing assembly without changing the switch differential, it is also possible to construct mechanisms according to the invention which have different switch differentials. This may be accomplished, as is explained below, by varying the distance X in comparison to the distance X It Will be observed from the general principles governing bodies rotating about an axis that when the lever 101 rotates about its axis 102 all points on the lever 101 make the same angular movement, but the actual distance which each point on the lever moves in a given angular movement is dependent upon the distance of that point from the axis. The sequential operation of the switches in the switching assembly 66 requires that the pressure plate 61 and the operating lever 56 be moved upward a certain distance between the actuation of the first switch and the actuation of the second switch, as previously described. Also, the forces F and F provided by the spring-loaded pressure assemblies 65a and 65b change as their coil springs are compressed in the upward movement of the pressure plate 61. In regard to these effects it has been found that when the distance X at which the switch assembly 60 acts upon the lever is greater than the distance X at which the speed translator 40 acts, the inherent switch differential of the switch assembly 60 is decreased. Conversely when the distance X is less than the distance X, the inherent switch differential is increased.

A further advantage, related to using a lever arm in Which X is greater than X is that switches having relatively greater movement actions may be used without correspondingly large vertical movements by the speed translator 40. This helps to avoid reduced accuracy and slow response to rapid changes in input speed which may occur where the speed translator 40 is required to make an extensive vertical movement.

While what has been described herein is considered at present to be a preferred embodiment of the invention, it is to be understood that this is merely exemplary of an arrangement in accordance with the invention and that variations and modifications may be made therein without varying from the principles thereof. Although the foregoing description relates to the operation of a single switch assembly 60 having a pair of switches, it is to be understood that the mechanism of the invention may utilize any number of switches or switch assemblies. Ac- 2O cordingly, it is intended to encompass within the scope of the appended claims all such variations and modifications as fall within the true spirit and scope of the invention.

1. A speed responsive switch mechanism including a housing, a rotatable shaft in said housing, a speed translation means the axial movement of which depends upon the speed of rotation of said shaft, an operating lever pivotally mounted at a fixed axis at one end to said housing, said translation means contacting said operating lever at a first point remote from said fixed axis, a pressure plate pivotally contacting said operating lever at a second point remote from said fixed axis, adjustable force means pivotally contacting said operating lever at a third point remote from said fixed axis, a pair of independently adjustable spring-load pressure assemblies contacting opposite ends, respectively, of said pressure plate, and a corresponding pair of switches actuated by said pressure plate, whereby said adjustable force means and said adjustable pressure assemblies acting at said specified points provide a wide adjustable range of rotatable speeds of said shaft at which said switches actuate.

2. The speed responsive switch mechanism of claim 1 wherein said third point is remote from said fixed axis a distance substantially greater than said first or second points.

No references cited.

BERNARD A. GILHEANY, Primary Examiner. 

1. A SPEED RESPONSIVE SWITCH MECHANISM INCLUDING A HOUSING, A ROTATABLE SHAFT IN SAID HOUSING, A SPEED TRANSLATION MEANS THE AXIAL MOVEMENT OF WHICH DEPENDS UPON THE SPEED OF ROTATION OF SAID SHAFT, AN OPERATING LEVER PIVOTALLY MOUNTED AT A FIXED AXIS AT ONE END TO SAID HOUSING, SAID TRANSLATION MEANS CONTACTING SIAD OPERATING LEVER AT A FIRST POINT REMOTE FROM SAID FIXED AXIS, A PRESSURE PLATE PIVOTALLY CONTACTING SAID OPERATING LEVER AT A SECOND POINT REMOTE FROM SAID FIXED AXIS, ADJUSTABLE FORCE MEANS PIVOTALLY CONTACTING SAID OPERATING LEVER AT A THIRD POINT REMOTE FROM SAID FIXED AXIS, A PAIR OF INDEPENDENTLY ADJUSTABLE SPRING-LOAD PRESSURE ASSEMBLIES CONTACTING OPPOSITE ENDS, RESPECTIVELY, OF SAID PRESSURE PLATE, AND A CORRESPONDING PAIR OF SWITCHES ACTUATED BY SAID PRESSURE PLATE, WHEREBY SAID ADJUSTABLE FORCE MEANS AND SAID ADJUSTABLE PRESSURE ASSEMBLIES ACTING AT SAID SPECIFIED POINTS PROVIDE A WIDE ADJUSTABLE RANGE OF ROTATABLE SPEEDS OF SAID SHAFT AT WHICH SAID SWITCHES ACTUATE. 